1. Field of the Invention
The present invention relates to an address database and an address retrieval system, and more particularly relates to a technology used for rapidly retrieving a desired geographic point.
2. Description of Related Art
Conventionally, an address retrieval system retrieving a desired geographic point by using an address database has been known. The point located by this address retrieval system is used for displaying a map centering on this point, searching for a route from the current position by using the point as a destination, and furthermore, retrieving a facility located around the point.
The address database used in such an address retrieval system has a tree structure composed of a plurality of hierarchies in which regional names ranging from large-area names to small-area names such as, for example, the names of the 47 prefectures of Japan, the names of administrative wards and cities, the names of administrative wards, town or village names, area names, and block numbers are caused to correspond to nodes, and the large areas are positioned at the hierarchical upper levels. In addition, the regional names of areas that are further larger than the 47 prefectures, for example, the regional names of Tohoku district, Kanto district, and Kinki district are occasionally used as the top hierarchical level.
In conventional address retrieval systems, a desired geographic point is located by using an address database having such a tree structure and sequentially narrowing down regional names from the regional names of a large area to the names of a small area, in other words, while sequentially tracing the nodes of the address database, for example, the prefecture→the administrative ward and city→the administrative ward→the town or village→the block number in the order.
In further detail, when the system is instructed to retrieve an address, the names of the prefectures are first displayed on the screen in list form in order to select a prefecture positioned at the top hierarchical level. The user selects a desired prefecture from among the names of the 47 prefectures displayed on this screen. When the desired prefecture is selected, after that the names of the administrative wards and cities belonging to the prefecture, positioned at the second hierarchical level, are displayed on the screen. Further, in a similar manner, the nodes are sequentially interactively traced about the name of town or village, the block number (chome) and so on, and the processing reaches the hierarchical bottom, thus specifying the desired region or geographic point to be located.
To give an actual example, when “2-chome Kitano-cho, Chuo Ward, Kobe City, Hyogo Prefecture” famous for “Ijinkan (Former Residences of Early Foreign Settlers)” is retrieved, the region is narrowed down by sequentially selecting the applicable regions according to the address notation “Hyogo Prefecture → Kobe City → Chuo Ward → Kitano-cho → 2-chome” in the order.
Further, as a technology relating to the address retrieval system, for example, JP-A-2003-186880 discloses an address retrieval system giving a map of an objective address or a map of the neighborhood of an objective address even when the user inputted an incorrect retrieval address character string, which is not registered in the database. In this address retrieval system, the user inputs the address of which the map is wanted into an address-retrieving server through an information terminal. The retrieving portion searches the address database, based on the inputted retrieval address character string, for the corresponding address data. Subsequently, the address retrieval system reads out the map data associated with the retrieved address data from the map database, and provides the user with the map data. When there exists no address corresponding to the retrieval address character string inputted by the user, the system repeats the retrieval while reducing the retrieval address character string from the rear by a predetermined amount each time (for example, by one character or by one address notation unit, up to a predetermined border) until one or more addresses are hit.
Moreover, as another technology relating to the system, for example, Japanese Patent No. 3267202 discloses a navigation device used for a vehicle, which retrieves a registered geographic point such as a destination or a passing geographic point by inputting the reading of the name of the registered geographic point or the character string of the name thereof. This navigation device for a vehicle includes: an information storing means for storing information about the reading of the registered geographic points as the registered geographic point information; an input means for inputting the reading of the registered geographic points; a transforming means for transforming the reading inputted by this input means into a predetermined character string; a retrieving means for searching the registered geographic points memorized in the information storing means for a registered geographic point of the name containing the transformed character string; and a display means for displaying the retrieved registered geographic points in list form. This makes easy the retrieval by the Japanese-syllabary (Japanese-alphabetical) input, resulting in excellent user-friendliness.
However, even if the user tries to retrieve an objective geographic point, the user often has an unclear knowledge about the intermediate portion of the address notation of the point, or memorizes only the town name. Accordingly, in the address retrieval system arranged as mentioned above, in the process of interactively selecting a regional name, if there exists a regional name that the user does not know or a little knows in any hierarchical level, the processing cannot reach the hierarchical bottom or must return to the hierarchical upper level and be restarted in the case of the user's selecting an incorrect regional name. As a result, it takes much time for the processing to reach the desired geographic point.
For example, when the “Ijinkan” mentioned above is retrieved, the memorizing patterns of the address information may be as follows:    (1) Only the town name of Kitano-cho is known.    (2) The town name of Kitano-cho is known, and it is known that the town is located at Kobe City in Hyogo Pref. In such a case, in the case of the memorizing pattern (1) of the address information, for example, the first hierarchical level of “Hyogo Prefecture” cannot be selected, failing in retrieving the point. In the case of the memorizing pattern (2) of the address information, the first and second hierarchical levels of “Hyogo Prefecture” and “Kobe City” can be selected; however, the ward name, which is the third hierarchical level, cannot be selected, also failing in retrieving the point.
For this reason, countermeasures are taken to display the regional names included by the hierarchical levels in list form. However, when a wrong regional name is selected from in the list, it is necessary to examine all the regional names included by the next lower hierarchical level to thereby realize that there exist no corresponding regional names therein; then to return to the higher level to select another regional name anew, and further, repeat a similar operation. In the above case of the memorizing pattern (2) of the address information, when the ward name, which is positioned at the third hierarchical level, is incorrectly selected, it is necessary to examine all the town names positioned in the next fourth level and thereby find that there does not exist the corresponding town name “Kitano-cho,” then return to the third level to newly select another ward name, and further, repeat a similar operation.
Memorizing patterns of address information probably include not only the above cases but also the case in which only a portion of an address is a key for finding a geographic point as in the case of “Aoyama 1-chome where a certain company exists” or “somewhere at Marunouchi,” for example. Therefore, there is a problem that when the user has unclear memory about an address, the user cannot retrieve the destination geographic point, or it takes much time for the user to retrieve the point.
The method of “Japanese-syllabary retrieval” performing retrieval by using only kana (the Japanese phonetic syllabaries) is known as a technique eliminating the problem of the above-described conventional address retrieval system. However, the “Japanese-syllabary retrieval” usually uses the names of facilities as the retrieval keys, and the system does not occasionally contain addresses. Moreover, even when the system contains addresses, because the number of facilities to be retrieved is tremendous, the number of characters to be inputted increases until selection from among many displayed candidates or display in list form can be performed. As a result, there is a problem that an input operation is troublesome.